Peel, core and slice the apples. Add the cinnamon and pour the lemon juice over them to stop them browning. Toss and set aside. Grease an 8½-inch cake tin.
Put the flour and sugar in a bowl, make a well in the centre and add the oil, vanilla essence, milk, eggs, and salt. Beat well to incorporate all the flour and form a smooth, thick batter. Pour the batter into the prepared cake tin.
Arrange the slices of apple on top of the batter, as you like. Sprinkle two tablespoons of cold butter, cubed, around the top of the cake and then sprinkle with sugar.
Bake for 30-40 minutes or until the apples are golden and the cake tester comes clean.
Serve each slice with a dollop of fresh whipped cream and a hot cup of coffee, or tea if you prefer.